Dielectric and Piezoelectric Properties of 0.91Pb(Zn1/3Nb2/3)O₃-0.09PbTiO₃ Single Crystals

The dielectric, piezoelectric and elastic properties of 0.91(PbZn 1/3 Nb 2/3 )O 3 –0.09PbTiO 3 single crystals have been investigated as functions of temperature and applied electric field. Two multiple phase transitions at 68°C and 178°C, the crystal changing from the rhombohedral ferroelectric phase to tetragonal ferroelectric and then to cubic paraelectric, have been observed. Both the transitions are of first-order, but both are slightly diffused. Significant increases in the dielectric, piezoelectric and elastic constants are observed at the lower transition point. In particular, the sample poled along the pseudo-cubic [001] axis reveals anomalously large piezoelectric and electro-mechanical coupling constants at room temperature in the rhombohedral phase ( d [001]// =1500×10 -12 C/N, k [001]// =0.92).